Almost everything we know about Olympus Mons comes from space missions. Here are some of the most important
MARINER 9
The novel feature of NASA’s Mariner 9 probe was a rocket engine powerful enough to place it in a stable orbit, allowing it to observe the planet at leisure. The previous successful Mars missions – Mariners 4, 6 and 7 – had only involved fleeting flybys, collecting a meagre 222 images between them. Mariner 9’s main objective was to photograph a large proportion of the Martian surface from close quarters over the course of several months. Unfortunately, when the spacecraft reached the Red Planet in November 1971, the entire planet was enshrouded in a global dust storm. This would have been a disaster for a flyby mission, but the orbiter was able to wait patiently for the dust to clear. When it did, it captured 7,329 images covering 80 per cent of the Martian surface, revealing a host of hitherto unknown features, including Olympus Mons and several other towering volcanoes.